Limits on testing for bird flu in humans could pose difficulty for containing spread The GuardianOfficials Solve Mystery Behind Human Bird Flu Case The Weather ChannelSerologic tests rule out avian flu in Missouri health workers; CDC confirms 2 Washington infections University of Minnesota Twin CitiesAs Bird Flu Spreads, Additional Human Infection Is Reported in Missouri The New York TimesCDC testing suggests Missouri did not see a cluster of bird flu cases STAT